There has been used in semiconductor manufacturing processes a processing apparatus for performing a process on a surface of an object to be processed while controlling a temperature thereof in an airtight processing chamber. FIG. 20 is a schematic cross sectional view showing an inside of a processing chamber of a conventional processing apparatus; and FIG. 21 is a schematic perspective view of a block for thermal transfer gas feed pipe.
As shown in FIG. 20, provided inside the processing chamber of the conventional processing apparatus is a lower electrode 10 also serving as a mounting table for mounting thereon an object to be processed, i.e., a semiconductor wafer W. An electrostatic chuck 12 for attracting and holding the semiconductor wafer W is installed on top of the lower electrode 10. A bottom portion of the lower electrode 10 is coupled with a grounded member 7 (e.g., an outer wall of the processing chamber) via an insulator 4.
There is provided between the electrostatic chuck 12 and the semiconductor wafer W a minute space (not shown) to which a thermal transfer gas for controlling the semiconductor wafer W to a specified temperature can be supplied, and the thermal transfer gas, e.g., a He gas, is supplied from a thermal transfer gas pressure control unit 68.
During a process, a high frequency power is applied to the lower electrode 10 and a plasma 50 is produced above the semiconductor wafer W. Meanwhile, e.g., a voltage V, which is identical to that generated between the lower electrode 10 and the plasma, is generated between the lower electrode 10 and the member 7 by the high frequency power.
Discharge may occur due to such voltage V, which induces electrons in the thermal transfer gas to accelerate in a thermal transfer gas feed pipe. Thus, in order to prevent such occurrence of discharge or the like, a block unit 64 for thermal transfer gas feed pipe is inserted in a portion of the thermal transfer gas feed pipe, wherein the thermal transfer gas is supplied via a thermal transfer gas feed pipe 60, the block unit 64 for thermal transfer gas feed pipe, and a thermal transfer gas feed pipe 62.
As shown in FIG. 21, the conventional block unit 64 for thermal transfer gas feed pipe is made of resin, e.g., Teflon (a registered trademark), and includes, e.g., three blocks 64-1, 64-2 and 64-3 for thermal transfer gas feed pipe having alternately formed holes. Resultantly, the voltage V is divided by as many as the number of the blocks for thermal transfer gas feed pipe. Further, every time the thermal transfer gas reaches an end portion of each block for thermal transfer gas feed pipe, the thermal transfer gas collides therewith to change the proceeding direction thereof and the energy of the accelerated electrons becomes lowered, which in turn prevents the discharge.
However, in a recent trend of high integration of semiconductor devices, there is a need for a processing under a condition of a higher voltage V. When a high voltage is applied in the conventional blocks 64-1, 64-2 and 64-3 for thermal transfer gas feed pipe, the thermal transfer gas may easily be discharged because the number of holes is large and further the thermal transfer gas is supplied in a substantially linear path.
In an effort to overcome such drawbacks, a greater number of blocks for thermal transfer gas feed pipe have been employed in the block unit 64 for thermal transfer gas feed pipe. However, as the number of blocks for thermal transfer gas feed pipe is increased, the pressure difference between a bottom surface of the semiconductor wafer W and a thermal transfer gas pressure control unit 68 increases, which deteriorates the responsiveness of the thermal transfer gas and as a result may render inaccurate control of the temperature of the object to be processed. Further, the conventional block for thermal transfer gas feed pipe is generally made of resin, e.g., Teflon, which may melt in a case of an occurrence of discharge.
The present invention has been conceived from the above drawbacks of the conventional processing apparatus; and it is, therefore, an object of the present invention to provide a novel, improved processing apparatus and a gas discharge suppressing member for use therein, capable of preventing the discharge of the thermal transfer gas and accurately controlling the temperature of the object to be processed.